Discharge apparatus



April "19.41- w. M. COODHUE ETAL DISCHARGE APPARATUS Filed June 16, 19375 Sheets-Sheet 1 M v 30 75 2 V 3/ 3/ v 35 A 36 Q 55 II as M M W]WITNESSES: INVENTORS g 0%. W/m'am M. Good/we A Roy 5.850 W61; Jr.

ATTORNEY April 2, 1941. w. M. eo'onnus EIAL 2,239,289

DI SCHARGE APPARATUS Filed June 16, 1937 5 Sheets-Sheet 2 WITNESSES:INVENTORS W 6? Mm W/l/fam M Good/we 6e fiay 15. Pom e1; Jr: 7% W BYATTORNE Patented Apr. 22, 1941 DISCHARGE APPARATUS William M. Goodhue,Boston, Mass., and Roy B.-

Power, In, Manhattan, Kans.

Applicationjune 16, 1937, Serial No. 148,616

26 Claims.

Our invention relates to electric discharge apparatus and has particularrelation to power supply apparatus. A de cription of our-invention,together with experimental data is published beginning on page 1200 ofthe November 1936, issue of Electrical Engineering.

It is an object of our invention to provide apparatus that shall operateas its own automatic regulator for supplying power from a source ofelectrical energy to a load.

Another object of our invention is to provide power supply apparatusthat shall incorporate a regulator which functions to maintain thepotential across the loadindependent 01' the potential of the source.

Still another object of our invention is to provide power supplyapparatus that shall automatically regulate itself to maintain the loadpotential constant in spite of variations in the source potential.

A further object of our invention is to provide power supply apparatusthat shall automatically regulate itself to maintain the load potentialconstant regardless of variations in-the load current.

A still further object of our invention is to provide power supplyapparatus by the operation of which it shall be possible to adjust thecompounding to any desired condition.

An additional object of our invention is to provide power supplyapparatus that shall automatically regulate itself to maintain the loadcurrent constant in spite of variations in the source potential. 1

A further additional object of our invention is to provide power supplyapparatus that shall automatically regulate itself to maintain the loadpotential substantially constant in spite o1 variations in the loadcurrent.

Another additional object of our invention is to provide a power supplyapparatus incorporating grid controlled electric discharge paths whereinthe discharge paths shall function to provide automatic regulation.

A more specific object of our invention is to provide a power rectifierthat shall operate as its own automatic regulator. ,I

An additional specific object of our invention is to provide apparatusof the type that shall opcrate as its own automatic regulator forrectifying the power supplied by a polyphae source to a direct currentload.

Another specific object of our invention is to provide a power supplysystem in which regulation shall be attained without the use of movablecontacts.

An ancillary object of our invention is to provide a highly tractablesystem for supplying power to an electro-dynamic machine.

Another ancillary object of our invention is to provide for an electricmotor a power supply system of such character that the operation of theelectric motor shall be adjustable with facility.

, A further ancillary object of our invention is to provide for anelectric motor a power supply system of such character that the speed ofthe motor shall be controlled by controlling a current of smallmagnitude. 7

A still further ancillary object of our invention is to provide a highlytractable power supply system for a direct current motor.

More generally stated, it is an object of our invention to provide apower supply system that shall be automatically regulable andadjustable, so that its operation may be made to conform to a widevariety of desired conditions. I

According to our invention, we interpose one or more discharge devicesor discharge paths, each of which has a control electrode and aplurality of principal electrodes and a gaseous medium, between thesource and the load. A constant potential of polarity such as toenergize the discharge device is impressed between the control electrodeand one of the principal electrodes. The magnitude of this potential isselected so large, compared to the critical control potential of thedischarge device, that random variations which may arise in themagnitude of the critical control potential of any one discharge deviceor between the critical control potentials of the different dischargedevices are substantially masked.

The critical control potential is defined as the potential between thecontrol electrode and a principal electrode of a discharge device atwhich the discharge device passes from a deenergized to an energizedcondition for a given potential between the principal electrodes. Forcontrol potentials more negative than the critical control potential,the discharge device if initially deemergized remains deenergized, formore positive control potentials it is energized.

0n the constant potential another potential dependent upon and, in.specific cases, proportional to the load potential is superimposed. Thelatter potential is of polarity opposite to the former potential and ofsuch magnitude that the critical control potential is only at timesexceeded.

Specifically when the source of electrical energy whereby the load is tobe supplied is of the polyphase type, a discharge device is insertedbetween each phase and the load and the aforementioned potentials areimpressed between the control electrode and a principal electrode ofeach of the discharge devices. In this case the total control potentialcomprising the sum of the two potentials mentioned above rises above thecritieal control potential periodically. We have found that whenproperly adjusted, a system of this type operates to maintain the loadpotential to the'former potential.

constant in spite of variations in the source poa tential.

Under certain conditions, it is desirable that the load potential shouldbe maintained constant independently of variations in the load current.At times the more general problem of compounding is involved. Theseproblems may be solved at the same time by superimposing on the twopotentials above mentioned a potential proportional to the load current.This potential may be derived by inserting current transformers in thesource and applying the rectified output or these transformers to thecontrol circuits of the discharge devices.

The foregoing procedure may be designated'as current compounding. Wehave also found that potential compounding may be of considerableutility in maintaining the load current or load potential or bothconstant independentlyof variations in source potential and the loadpotential constant independently of variations in The electro-dynamicmachine is supplied from a source through discharge devices of thegaseous type. In the control circuits of the discharge devices, aconstant potential of magnitude large compared to the critical controlpotential and of vices is impressed. On this potential another p tentialderived from current transformers in the power source and essentiallyproportional to the current through the machine is superimposed. Thelatter potential is of opposite polarity We have found that a machinesupplied in this manner operates at a substantially constant currentindependently of variations in potential as long as the potential v ofthe source is sumcient to supply the potential of the machine, and ate.substantially constant potential independently of the variations in.current when the potential of the source is insuffi cient to supply thepotential of the machine. During starting, therefore, an electro-dynamicmachine supplied in this manner operates in the first region mentionedabove, while during its normal functioning it operates in the otherregion mentioned above. The system discussed above may be applied withparticular advantage where a direct-current motor having independentexcitation is supplied from a polyphase alternating source. Such a motormay be controlled by controlling i'ts excitation and this object may beaccomplished by varying the small current delivered by a photo-electriccell.

The novel features that we consider charactcristic of our invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and its method ofoperation, together with additional objects and advantages thereof, willbest a polarity such as to energize the discharge deaaeaaee specificembodiments when read in connection with the accompanying drawings, inwhich:

system such as is disclosed in Fig. 3 under certain circumstances; IFig. 5 is a diagrammatic view of a modification of our inventioninvolving the application of the principles illustrated in Fig. 4 to anelectrodynamic machine;

Fig. 6 is a diagrammatic view showing a modification of our invention asdisclosed in Fig. 5;

Fig. 'l is a graph showing further features of the modification shown inFig. 3;

d is a diagrammatic view of a modification of our invention involvingboth current and po tential compounding, and;

Fig. 9 is a diagrammatic view of a modification of our invention as itis applied to a double three-phase rectifier system.

The apparatus shown in Fig. 1 comprises a polyphase source ii, theoutput of which is connected to a suitable supply transformer l3. Thesecondary it: of the transformer 53 is connected in star and supplies aload ll through a plurality of discharge devices l9, 2! and 23, adischarge device being interposed between each of the windings 25, 2'!and 28 of the secondary and one terminal of the load. The other terminalof the load I! is connected to the neutral point 29 of the secondary l5through a reactor 30. Each of the discharge devices l9, 2i and 23comprises an anode 3!, a hot cathode 33, a control electrode 35 and asuitable ionizing medium. The ionizing medium may be provided by aninert gas such as argon or neon at a pressure of 2 or 3 millimeters ofmercury or it may be the vapor of a mercury globule located within thecontainer of the discharge device.

,Each of the discharge devices I9, 2| and 23 has a so-called arc-likecharacteristic. One aspoet of such a characteristic is abruptness ofresponse. For a given anode-cathode potential,

, the device is substantially nonconductive as long as thecontrol-electrode-cathode potential is more negative than a potentialwhich we have above designated as the critical control potential. Whenthe control-electrode-cathode potential becomes more positive than thecritical control potential, the discharge device becomes conductive andpasses current, the magnitude of which is independent of the extent towhich the critical conbe understood from the following description oftrol potential is exceeded. Another aspect of the arc-likecharacteristic is the so-called lock-in feature. A discharge device ofthe arc-like type when once rendered conductive continues to re mainconductive regardless of the control electrode potential as long as theanode-cathode potential is sumcient to support the discharge.

As regards the foregoing comments, it is to be noted that they representthe. general situation. Discharge devices which are responsive tovariations in the control potential have been developed andwhere asystem including such a discharge device involves the practice of ourinvention, we intend that it shall 'be regarded as lying within thescope thereof. 'It is to be noted, moreover, that while in Fig. 1 and inthe other views our invention is illustrated as applied to -hot cathodedischarge devices l3, 2| and 23, it

may also be utilized with discharge devices in which cathodes of othertypes are utilized. For example, the hot cathode 33 may be replaced by amercury pool or a deposit of lead or cadmium or any other metal which iseither continuously maintained energized by a keep-alive electrode or isreenergized at suitable intervals by a makealive electrode operatingsomewhat as a control electrode." The make-alive electrode may beexternal to the container of the discharge device or it may be internaland in contact with the pool or deposit as in the Ignitron tubes. Thehot cathode 33 may also be replaced by a so-called cold cathode as inthe Westinghouse cold cathode Grid Glow tube designated as KU-618 in theart. Apparatus incorporating discharge devices of the type justmentioned in lieu of the devices l9, 2| and 23 and involving the generalfeatures of our invention are within the scope thereof.

The control electrodes 35 of the discharge devices |9, 2| and 23 areconnected through suitable resistors 31, 33 and 4| to a common point 43.The cathodes 33 of the discharge devices are also connected to a commonpoint 45 which is the same electrically as the positive terminal ot theload l1. Between the common control-electrode point 43 and the commoncathode point 45 a composite control potential is impressed. Onecomponent of this potential is applied by a directcurrent source such asa battery 41. The positive terminal of the source 41 is connected to thepoint 43 and its negative terminal is connected to the variable tap 49of a potentiometer 5| connected across the load |I.' The source 41 is ofa magnitude that is large compared to the critical control potential ofthe discharge devices l9, 2| and 23 and the relationship in themagnitude of the quantities is such that the random variations incritical control potential which arise in a single discharge device is,2| or 23 or between the different discharge devices are substantiallymasked.

The other component of the control potential is provided between themovable tap 43 of the potentiometer 5| and the cathode common point 45.The latter potential is of such magnitude and polarity that the totalpotential exceeds the critical control potential periodically atintervals depending on the magnitude of the power which is to besupplied to the load H. I I

The system operates to automatically maintain the potential supplied tothe load i1 independent of variations in the potential of the source Thefunctioning of the apparatus is illustrated in Fig. 2. In curve A ofthis view, the potential difierence between the cathode 33 of anenergized discharge device and the neutral point 23 is plotted as afunction of time. It will be noted that inasmuch as the potential dropthrough the.

discharge devices it, 2| and 23, when they are energized, iscomparatively small, this plot represents substantially the potentialssupplied between the neutral point 29 and the terminals of the secondarywindings 25, 27 and 29 oi the tranw former i3.

Potential is plotted vertically and time hori zontally. The abscissarepresents the potential of the neutral point 25.. The heavy lineportions of the full line half waves in curve A represent a normalcondition of operation. The heavy line portions 59 oil the broken linehalf waves hi represent a hypothetical condition which exists when anincrease occurs in the potential of the source it corresponding to thedifference between the heights of the'broken line curves 55 and the fullline loops 59.

- an essential feature of our invention arises.

When the apparatus is in operation, the discharge device |9, 2l or 23,corresponding to each phase, is conductive until the discharge devicecorresponding to the subsequent phase is energized. The loop portions 53and 59 represent the conductive conditions of the successive dischargedevices when the source potential corresponds respectivelyto loops55-and'6i. During a short transition period the discharge device (sayl9) which is being extinguished and the discharge device (say 2|) whichis being energized are both conductive simultaneously. The transitioninterval is known as the commutation period and is represented in curveA by the two vertical lines 63 and 65 which are separated by asubstantially horizontal line 61 between each pair of portions 53 ofloops 55 and by corresponding lines 69, H and 13 for loops 5|.

The successive discharge devices It, 2| and 23 are, of course, notenergized at random. Each discharge device is in its turn renderedconductive at the instance when the total control potential exceeds thecritical control potential. It is from the timing of the occurrence ofthis event that It happens that for the potentials represented by thebroken line loops 6|, this instant occurs later than for the potentialsrepresented by the full line loops 55 and the timing is such that theload potential remains constant. This aspect of our invention can be.seen from the other curves shown in Fig. 2.

In curve B the potential between the cathodes 33 and the conductor 15from, the load I! to the reactor 30 is plotted as a function of time.Again potential is plotted vertically and time horizontally. Theabscissa now, however, corresponds to the potential of conductor 15. Thefull line loops I1 correspondto the full line loops 53 of curve A andthe broken line loops I9 correspond to the broken line loops Bl of curveA. The potential variations are not as irregular as those represented incurve A by reason of the smoothing effect of the reactor 3|), and thecorresponding loops '1! and 19 are, therefore, not so jagged as thecorresponding loop portions 53-53-t'|-65 and 53-99-l3-l|.

Since the cathodes 33 are connected to a common point 45, the waves TIand 19 in curve B correspond to the potential difference between thepoint 45 and the conductor 15 and, therefore, between the lower terminaland the upper terminal of the potentiometer 5|. The actual potentialimpressed between the control electrodes and the cathodes 33 ofthedischarge devices it, ill and 23 includes a potential derived frompoten-= tiometer iii and may be derived from curve B. It is illustratedin curve 0. Here potential is again plotted vertically and timehorizontally, but the abscissa corresponds to the potential oi thecathodes The horizontal line i'li above the abscissa corresponds to thepotential supp' ed by the battery 62' in the control circuit. .Il' lineloops and the broken line loops medium weight at considerable distancehell the abscissa correspond, to the potential. di between the movableoi the pate-mic 5t and the cathodes The horizontal i just below thecissa correwonds to the control potent-m o). the discharge devices.heavy full line and broken line loops an correspond to t e sum of thepotential. d from the potentiometer and the intersectthe criticalcontrol potential line at nodal points 93 and 95, respectively, whichcorrespond to the transition from one energized discharge device l9, 2!or 123 to the subsequent one.

The curves of Fig. 2' represent the natural operation of the apparatus.Consider the full line heavy loop 89 on the extreme left of curve C,assuming at the same time that the potential applied to the dischargedevices [19, 2|] and 23 corresponds to half wave 55a. In correspondencewith the left-hand loop $39, the control potential impressed on thedischarge devices rises from a value substantially below the criticalpotential to the value of the critical potential represented by thesecond nodal point 93 from the left. During all this time one ofthedischarge devices (say iii) which corresponds to the first phase hasbeen energized and the current transmitted therethrough has swelled anddecreased in accordance with loop portion 5a. At the instantcorresponding to the second nodal point from the left, the dischargedevice (say 25) corresponding to the second phase 2? is energized, sincethe anode cathode potential applied to it is greater than theanode-cathode potential applied to the first phase. The correspondingcontrol potential now becomes more negative, as illustrated, by thecentral heavy full line wave 38 as the current 'fiow through the loadincreases, then it becomes more positive as the current decreases, untilthe 111 stant corresponding to the third nodal point 33. Here thedischarge device (say 23) corresponding to phase 28, is energized andthe above procedure again repeated, producing the condition representedby the right-hand loop 89. The energize.- tion of device 23 is followedby the energization of device I 9, and the above described steps arethus repeated until the current flow is for some reason interrupted orchanged. If a condition corresponding to the broken line loops BIexists, the critical control potential line 81 will be out at a laterinstant as is illustrated by the broken line loops 9i and the nodalpoints 95 and the ignition of thedischarge devices will becorrespondingly delayed. It is apparent that the load potential will nowassume avalue smaller than would be expected from the increase in sourcepotential and in actual practice we have found that the, load potentialremains substantially constant.

While the fact thatthe load potential is constant in spite ofvariations-in the source potential has been demonstrated by usconclusively by experiment, it may also be demonstrated mathematically.

Let

E=the potential of the battery 4i, V=the load potential, e =the controlpotential,

a=8 fraction represented by the setting of the potentiometer 5|,

then at the nodal points: i

eg=EdV fl of the order of 12 volts. In one application of our inventionwe have utilized discharge devices of the type that have a criticalcontrol potential oi plus 12 volts, and we have used a battery potentialof 90 volts. It is to be noted that for a critical control potential ofplus 12 volts, the critical control potential line 931? of curve C wouldbe above rather than below the time axis.

Where the load current is to he maintained independent of variations inthe load poten tial or is to vary in a predetermined manner with theload potential, the simple arrangement shown in Fig. i does not sufiiceand the arrangement shown in Fig. 3 should be utilized. In themodification shown in Fig. 3, the elements of Fig. l are incorporatedand in addition a potential substantially proportional to the loadcurrent is superimposed on the battery potential and the potentiometerpotential. The latter potential is derived from the source it throughcurrent transformers 97!, 951 and ifll coupled to the conductors M3,565, and till, respectively, from the source to the primary I99 of the,supply transformer it. The transformers ill, 99 and till supply avariable resistor Hi through a plurality of rectifiers H3, H5 and Ill.

A variable capacitor M9 is connected between the movable tap 02!] of theresistor iii and one of its terminals. The capacitor H9 operates tosmooth out the potential supplied by the transformers 91,

' 99 and I8! and may on occasions be omitted entirely.

The movable tap 62B of the resistor I II and its left-hand terminal areconnected in the control circuit of the discharge devices I9, 2! and 23through a suitable reversing switch I23, so that the potential derivedfrom the resistor may have either a-positive or a negative polarity inthe control circuit depending on the position of the switch. Thepotential impressed by reason of the current flow through the resistorIII is to a fair approximation proportional to the load current, andthus operates to provide the necessary compensation for the variationsin the current. For

'proper adjustment of the resistor l I I and the reversin switch I23,the load potential may be rendered substantially constant in spite ofvariations in the load current. This condition is designated in the artas net compounding. Difierential compounding or cumulative compoundingmay be attained by properly raising the magnitude of the potentialsupplied by the resistor HI and closing the reversing switch I23 so thatthe potential supplied is of the proper polarity. Thus it is seen thatany desired characteristic for the supply'of power to the load I1 may beattained.

Using an arrangement such as is shown in Fig. 3, but with the movabletap 49 of the potentiometer SI connected to the common cathode point 45,we have made measurements of the directcurrent load potential as a.function of the directcurrent load current for various magnitudes o! theresistor III through which the compounding potential is supplied.Certain of the results of these measurements are shown in Fig. 4, inwhich the direct-current load potential is plotted as a function of thedirect-current load current. Potenltial is plotted vertically andcurrent horizon- Three curves I25, I21 and I29 are reproduced, the curveI25 on the extreme left representing a large value of resistance, thecenter curve I21 9.

' medium value of resistance, and the curve I29 on 1 Fig. 3 with thepotentiometer potential zero as a rather interesting characteristic. Upto a ertain potential 01 the order of 280 volts, the curent issubstantially constant as the potential is icreased and the condition isrepresented by subtantially vertical lines I31, I33 and I35. Above hispotentialthe potential is substantially contant as the current decreasesand the condition 5 represented by substantially horizontal lines 37,I38 and MI. The latter portion of the curves epresents the conditionwhich exists in the sysem when at a given current the load potentialecomes so large that the source potential is inufdcient to maintain thecurrent. The lines I3I, 33 and I35 represent the condition when for a:iven current the load potential is of such magniude that the sourcepotential is sufficient to naintain the current.

The property of the apparatus that is illus- ;rated in Fig. 4 may withadvantage be utilized .n a system such as is shown in Fig. 5. In thenodification shown in this view, the armature I43 of a direct-currentmotor I45 with independent excitation I41, is supplied from the out- Iout of a system such as is shown in Fig. 3. The

force) increases. The potential continues to increase with the currentconstant until the motor I45 attains its operating speed.- .At thispoint the system operates along the lines I31, I39 or I, and the loadpotential becomes constant; that is to say, the back electromotive forceof the motor and its speed become substantially constant.

Accordingly, an analysis of the curves I25, I27! and I29 as they applytothe system shown in Fig. 5 reveals that during the starting period thecurrent drawn by the motor M5 is substantially constant, and, therefore,the torque is constant. During the operating period, the potential issubstantially constant and although the current may vary, the speedremains substantially constant. In a system such as is shown in Fig. 5,starting equipment is eliminated and the torque may be high becausenormal direct-current motors such as I45 may be used at potentials forarmature of the motor is connected between the reactor and the commonjunction point 45 of the cathodes 33. The exciting winding 8 of themotor is supplied independently from the main source through anauxiliary transformer I5I '(or a source of any other type) and throughan auxiliary discharge device 553. The latter may be a gaseous or a highvacuum tube having an anode I55, 2. hot cathode I51 and a controlelectrode I530: any other discharge device of the various typesmentioned hereinabove. The discharge device I53 is controlled through aphoto-electric cell I5! connectedbetween its control electrode I59 anditsanode 555. By varying the radiation impinging on the photo-electriccell I5I,'the potential impressed between the anode I55 and the controlelectrode I59 is varied and thus the excitation of the motor, and,accordingly, its speed is controlled.

In lieu of the resistor III and the reversing switch I23 of theapparatus shown in Fig. 3, an

auxiliary potentiometer I53 with a center tap I and a variable tap I61,which may be displaced on both sides of the center tap is utilized. Bysliding the movable tap I61 from one side of the center tap I65 to theother, the polarity of the potential impressed from the currenttransformers may be varied. However, as a general rule, we prefer tooperate with the potential supplied by the potentiometer I53 oi theopposite polarity as the potential supplied by the battery I".

It is seen that the energy consumed by the motor I may be controlled byshifting the movable tap of the potentiometer I83.

Depending upon the resistance of the auxiliary potentiometer I33 that isin the control circuit of the discharge devices I9, 2i and 23, the motorI55 has a. characteristic corresponding to one or the other of thecurves I25, I2'I or I29, reproduced in Fig. 4. When power is firstapplied to the system, the'mctor begins to rotate and its speedgradually increases for an interval of time that may be designated asthe starting period. During the starting period the system is operat-Ing along the lines I3I I33 or I35 and the motor draws constant currentof a predetermined value, depending on the resistance in the controlcircuit, while the potential manifested at the terminals of the armatureI43 (the peak electromotive which they are best adapted; The speed maybe controlled by controlling the field excitation and this object may beaccomplished by utilizing an element of such small space and powerrequirements as a photo-electric cell ISI. I

In accordance with the foregoing principles, the maximum permissibletransient load torque is equal to the starting torque. The latter may beset by the operator with the potentiometer I53 in the control circuit,and as is the usual case, may be of from 1 to 3 times the normal torque.The starting current may be reduced at any time below the maximumpermissible value by inserting a. resistor I55 in series with thepotentiometer I53 as is illustrated in Fig. 5 for example. The resistorits in the modification shown in Fig. 6 may be connected in the circuitafter the ,motor has started by asuitable two pole switch Ill. Themovable contactor IIfibf the switch III is connectedto the movable tapIfil of the auxiliary potentiometer I53, one pole H5 is connected to thecontrol electrode common point t3 and the other pole IT! is connected toone terminal of the resistor I59, its other terminal being connected tothe point 43.

In Fig. 7, the load current for a system, such as is shown in Fig. 3, isplotted as a function of the potential of the battery d1 for thecondition in which the potential supplied by the main potentiometer 5iis zero. Current is plotted ver-' tically and potential horizontally.The upper curve I13 represents the variation in direct-current as afunction oi the battery potential for a short circuit across the loadterminals andthe lower curve Itl represents the function for a finiteload II--speciflcally 58 ohms. The short circuit curve I13 is ofparticular interest. The current output varies continuously without anycritical points from zero to a considerable value. This property of theapparatus which may be important in such applications as welding, forexample, cannot be obtained with any other arrangement known to us thanthe one disclosed here. An ordinary phase shift controlled rectiher iscritical to the phase adjustment when the loadis a short circuit. Insuch a case, the output current of the rectifier is small for certaindegrees phase angle and attains full value for a variation of 2 0r 3degrees in phase from this value.

It may be that other conditions of operation are desired than the onesdiscussed heretofore. For example, it may be'desired that the loadcurrent should remain constant independent of variations in the sourcepotential. Another characteristic which is sometimes desired in practiceis a load potential which is constant independent of variations in theload current. Both of these conditions may be attained by utilizingso-called potential compounding alone or in combination with currentcompounding.

An arrangement incorporating this feature is shown in Fig. 8. Inaddition to the potential derived from the current transformers 97], 99and WE, the battery potential and the potentiometer potential, apotential is impressed in .the control circuit of the discharge deviceswhich is derived from an auxiliary potential transformer M33. Thetransformer 583 is oi the ordinary delta-star type and supplies a secondauxiliary potentiometer 885 through rectifiers it'll, 689 and tea. The

potentiometer E85 is provided with a variable tap 9% which is connected.to the common point oi .the control electrodes 35, one of its terminaltaps is connected to the neutral point we of the secondary it'll of theauxiliary transformer i333 and the other to the poles B98 and 2M of thereversible switch it?! through which the potential derived from thecurrent transformers 917, Qt and Hill is impressed in the controlcircuit. The potential derived from the potential transformer 883 isthus superimposed on the other potentials in the control circuit. If, asis the case at times. it is desirable that only potential compounding beutilized, the resistor iii supplied from the current transformers S1, 99and Hill may be short circuitedby moving the movable tap to the upperterminal. However, in general, both current compounding and potentialcompounding is desirable, so that potential is supplied by both thecurrent transformers and the auxiliary potential transformer. I

Our invention may also'be applied to a system in which two sets 263 and205 of three discharge devices 20?, 239 and 2M and 263, M and M77, eachare interposed between the load El and the source. In such a case atransformer 2H8, with a double Y secondary M9 is utilized and thedischarged devices 201, 2%, 22M, 283, M5 and it? are connected to thewindings 222i, 223, 225, 227?,

229 and 23! of the secondary. The potentials are supplied in the controlcircuits of the discharge devices in the same manner as in the single Yarrangement shown in the other views through potentiometer 5! with thevariable tap 49 and the Our invention has been disclosed herein as.

applied to various systems. A number of changes can be made in thesesystems without departing from the scope of our invention. It is to benoted, for example, that the combination of thevariablecurrent-compounding resistors i H and the reversing switches I23 may beeverywhere replaced by variable potentiometers 053, such as areutilized, for example, in the modifications shown in Figs 5 and 6. I

In the modification shown in Fig. 9, a. number of changes may be madeand for that matter the changes may be added to the other modificationsin cases where they areof advantage. One change which we regard as ofsome importance is accuses the insertion of an alternating currentpotential in the individual control conductors of the discharge devicestill, 209, Hi, M3, M5 and 2H. For this purpose a so-called gridtransformer may be utilized. It may consist of a star-connectedarrangement with 6 windings. Each of the windings may be connected inthe conductor leading from a control electrode resistor 2 35, 24?, 249,25 I 253 and 255, respectively, and the neutral point may be connectedto the conductor 25? which in 'Fig. 9 is connected to the variable tap8533 of the potential compounding potentiometer N35. The remainder ofthe connections to the variable tap 69 of the main potentiometer 5i andthence to the load ill may be the same as shown in Fig. 9.

Finally it is to be noted that while the discharge devices it, it, 23,2M, 209, 2M, M3, 2!!) and 2!]? are shown as discrete elements, they mayat times be replaced by discharge paths, all or some of which may bedisposed in a common container and one or more electrodes Si, 33 or 35of which may be common to all or some of the paths.

Although we have shown and described certain specific embodiments of ourinvention, we are fully aware that many modifications thereof arepossible. Our invention, therefore, is not to be restricted exceptinsofar as is necessitated by the prior art and by the spirit of theappended claims.

We claim as our invention:

1. Apparatus for supplying power from a source of electrical energy to aload comprising a disv charge path having a plurality of principalelectrodes and a control electrode and a gaseous Hiedium interposedbetween said source and said load, said. load being supplied throughsaid discharge path, means for impressing a. potential of one polaritybetween said control electrode and one of said principal electrodes,said potential being of a magnitude that is sufliciently large to maskrandom fluctuations in the critical potential of said discharge path andmeans for superimposing a potential, dependent on the magtrodes and acontrol electrode and a gaseous medium interposed between said sourceand said load, said load being supplied through said discharge path,means for impressing a potential between said control electrode'and oneof said principal electrodes of a polarity such as to tend to energizesaid discharge path, said potential being of a. magnitude that issufficiently large to mask random fluctuations in the critical controlpotential of said discharge path and means for superimposing apotential, dependent on the magnitude of the output potential supplyingsaid load and of opposite polarity to said first-named potential, onsaid first-named potential, said last-named potential being of suchmagnitude that the critical control potential of said discharge path isat times exceeded.

3. Apparatus for supplying power from a source of electrical energy'toa. load comprising a discharge path having a plurality of principalelectrodes and a control electrode and a gaseous medium interposedbetween said source and said load, said load being supplied through saiddischarge path, means for impressing a potential.

on said first-named potential, said last-named potential being of suchmagnitude that the critical control potential of said discharge path isat times exceeded and means for superimposing on said first-named andsecond-named potentials a potential dependent on the current flow fromsaid source.

4. Apparatus for supplying power from a source of electrical energy to aload comprising a discharge path havinga plurality of principalelectrodes and a control electrode and a gaseous medium interposedbetween said source and said load, said load being supplied through saiddis charge path, means for impressing a potential of one polaritybetween said control electrode and one of said principal electrodes,said potential being or amagnltude that is so large as to mask randomfluctuations in the critical potential of said discharge path, means forsuperimposing a potential, dependent on the magnitude of the.

medium interposed between said source and said load, said load beingsupplied through said discharge path, means for impressing a potentialof one polarity between said control electrode and one of said principalelectrodes, said potential being of a magnitude that is so large as totrol potential of said discharge path, means ior A superimposing apotential, dependent on the magmask random fluctuations in the criticalcontrol of opposite polarity to said first-named potenan, on saidfirst-named potential, said'last- V named potential being ofsuchmagnitude that the critical control potential of said discharge pathis at times exceeded, means for superimposing on said first-named andsecond-named potentials a potential dependent on the current flow fromsaid source, and means for superimposing on all said potentials apotential dependent on the potential of said source when power is beingsupplied to said lead.

Apparatus for supplying power from a source of electrical energy to aload of the type that requires a predetermined compounding comprising adischarge path having a plurality of principal electrodes and acontrol'electrocle and a gaseous medium interposed between said sourceand said load, said load being supplied through said discharge path,means for impressing a potential of one polarity between said controlelectrode and one of said principal electrodes, said potential being ofa magnitude that is suiliciently large to mask random fluctuations inthe critical connitude of the output. potential of said load and ofopposite polarity to said first-named potential, on said first-namedpotential, said last-named potential being or such magnitude that thecritical control potential of said discharge path is at times exceeded,means iorsuperimposing on said first-named and second-named potentialsapotential dependent on the current flow from said source, and means foradjusting the last said potential to select a particular compounding forsaid load.

source and said load, said load being supplied through said dischargepath, means for impressing a potential oi one polarity between saidcontrol electrode and one of said principal electrodes, said potentialbeing of a magnitude that is so large as to mask random fluctuations inthe critical control potential of said discharge path and means forsuperimposing a potential, dependent on the magnitude of the outputpotential supplying said load and of opposite polarity to saidfirst-named potential, on said first-named potential, said last-namedpotential being of such magnitude that the critical control potential ofsaid discharge path is periodically exceeded.

8. Apparatus for supplying power from a periodic current source ofelectrical energy to a load comprising a discharge path having aplurality of principal electrodes and a control electrode and a gaseousmedium interposed between said 'source and said load, said load beingsupplied through said discharge path, means for impress ing a potentialof one polarity and oi substantially constant magnitude between saidcontrol electrodeand one of said principal electrodes, said potentialbeing of a magnitude that is so large as to mask random fluctuations inthe critical control potential or said discharge path and means forsuperimposing a potential, dependent on the magnitude of the outputDotential supplying said load and of opposite polarity to saidfirst-named potential, on said first-named patch tial, said last-namedpotential being of such magnitude that the critical control potential ofsaid discharge path is periodically exceeded.

9. Apparatus for supplying power from an alternating current source ofelectrical energy to a load comprising a discharge path having aplurality of principal electrodes and a control electrode and a gaseousmedium interposed between said source and said load, said load beingsupplied through said discharge path, means for impressing a potentialor one polarity between said control electrode and one of said principalelectrodes, said potential being of a magnitude that is so large as tomask random fluctuations in plurality of principal electrodes and acontrol electrode and a gaseous medium interposed between each phase ofsaid source and said load, said load being supplied through saiddischarge path, means for impressing a potential of one polarity betweenthe control electrodes and one of the principal electrodes of all ofsaid discharge paths, said potential being of a magm tude that is solarge as to mask. random fluctuations in the critical control potentialof said dis charge paths and means for superimposing a potential,dependent on the magnitude of the output potential supplying said loadand of op posite polarity to said first-named potential, on saidfirst-named potential,- said last-named potential being of suchmagnitude that the critical control potential or" said discharge pathsis periodically exceeded by the total potential.

11. Apparatus for supplying power from a polyphase source of electricalenergy to a direct current load comprising a discharge path having inefiect an anode, a cathode and a control electrode and a gaseous mediuminterposed between each phase of said source and said load, said loadbeing supplied through said discharge paths, means for impressing apotential of positive po-= larity between the control electrodes and thecathodes of all said discharge paths, said potential being of amagnitude that is large compared to the critical control potential orsaid discharge paths and means for superimposing on said positivepolarity potential a potential of negative polarity, that varies independence upon the variation of the output potential supplying saidload, and that has a magnitude such that the control potential of saiddischarge paths is periodically exceeded by the total potential.

12. Apparatus according to claim 11 characterized by the fact that thepositive polarity potential is of such magnitude that it masks thevariations of the critical control potential arising in any onedischarge path or between the discharge paths.

13. Apparatus for supplying power from a poiyphase source of electricalenergy to a directcurrent load comprising a discharge path having ineffect an anode, a cathode and a control electrode and a gaseous mediuminterposed between each phase of said source and said load, said loadbeing supplied through said discharge paths, means for impressing apotential of positive polarity between the control electrodes and thecathodes of all said discharge paths, said potential being of a.magnitude that is so large as to mask random fluctuations in thecritical control potential of said discharge paths, means forsuperlmposing on said positive polarity potential a potential ofnegative polarity, that varies in dependence upon the variation of theoutput potential supplying said load, and that has a mag= nitude suchthat the critical control potential oi said discharge paths. isperiodically exceeded by the total potential and means for superimposingon said potentials of positive and negative polarlty a. potentialdependent upon the magnitude aaaaaso charge paths, means for impressinga potential of the load current to compensate for load cur- 4 pathhaving in effect an anode, a cathode and a control electrode and agaseous medium interposed between each phase of said source and'saidload, said lead being supplied through said dis- 'of positive polaritybetween the control electrodes and the cathodes of all said dischargepaths, said potential being of a magnitude that is sufllciently large tomask random fluctuations in the critical control potential of saiddischarge paths, means for superimposing on said positive polaritypotential 8. potential of negative polarity, that varies in dependenceupon the variation of the output potential supplying. said load, andthat has a magnitude such that the control potential or said dischargepaths is periodically exceeded by the total potential and means forsuperimposing'on said potentials of positive and negative polarity ispotential dependent upon the magnitude of the load current to adjust thecompounding.

15. Apparatus for supplying power from a polyphase source of electricalenergy to a directcurrent load comprising a discharge path having ineffect an anode, a cathode and a control electrode and a gaseous mediuminterposed between each phase or: said source and said load, said loadbeing supplied through said discharge paths, means for impressing apotential of positive polarity between thecontrol electrodes and thecathodes of all said discharge paths, said potential being of amagnitude that is so large as to mask random fluctuations in thecritical control potential of said discharge paths, means forsuperimposing on said positive polarity potential a potential ofnegative polarity, that varies in proportion with the output potentialsupplying said load, and that has a magnitude such that the criticalcontrol potential oi said discharge paths is periodically exceeded bythe total potential and means for superimposing on said potentials ofpositive and negative polarity a potential proportional to the magnitudeof the load current to compensate for load current variatiohs,

16. Apparatus for supplying power from a source of electrical energy toan electrodynamic machine having an armature and independent excitationmeans comprising an electric discharge path having a control electrodeand a plurality of principal electrodes and a gaseous medium, interposedbetween said armature and said source, said armature being suppliedthrough said discharge path, means for impressing a potential ofmagnitude sufilciently large to mask random fluctuations in the criticalcontrol potential of said discharge path between said controlelectrodeand one of said principal electrodes and means for superimposing on saidfirst-named potential a potential dependent on the magnitude of thecurrent flow through said armature.

1'7. Apparatus for supplying power from a source of electrical energy toan electro-dynamic machine having an armature and independent excitationmeans, comprising an electric discharge path, having a control electrodeand a plurality of principal electrodes and a gaseous medium, interposedbetween said armature and said source, said armature being suppliedthrough said discharge path, means for impressing a potential ofmagnitude sufliciently large to mask random fluctuations in the criticalcontrol potential of said discharge path between said control electrodeand one of said principal electrodes and means for superimposing on saidfirst-named potential 9. potential proportional to the magnitude of thecurrent flow through said armature up to armature potentials ofmagnitudes for which the potential of the source is sumcien't. 1

18. Apparatus for supplying power from an alternating current source oielectrical energy to an electro-dynamic machine having an armature andindependent excitation means, comprising an electric discharge path,having a control electrode, an anode and a cathode and a gaseous medium,interposed between said armature and said source, said armature beingsupplied through said discharge path, means for impressing a potentialof magnitude suillciently large to mask random fluctuations in thecritical control potential of said discharge path and of positivepolarity between said control electrode and said cathode and means forsuperimposing on said first-named potential a potential of negativepolarity dependent on the magnitude of the current flow through saidarmature.

19. Apparatus for supplying power from a polyphase source electricalenergy to an electro-dynamic machine having an armature and independentexcitation means, comprisingin eiiect an electric discharge path, havinga control electrode, an anode and a cathode and a gaseous medium,interposed between said armature and each phase of said source, saidarmature being supplied through said discharge path, means forimpressing a potential of magnitude so large as to mask the variationsarising in the critical control potential of each said discharge pathand between the critical control potentials of all said discharge pathsand of positive polarity between the control electrode and the cathodeof all said discharge paths and means for superimposing on saidfirst-named potential a potential proportional to the magnitude of thecurrent iiow through said armature up to armature potentials ofmagnitudes for which the potential of said source is sufllcient.

20. Apparatus according to claim 19 characterized by photo-sensitivemeans for controlling the excitation of the machine.

21. Apparatus for varying the supply at power from a source 01alternating current to a load of the type that has the properties of ashort circuit comprising an electric discharge path having a controlelectrode and a plurality of principal electrodes and a gaseous mediuminterposed between said source and said lead through which current flowsto said load, means for impressing a -potential, proportional to thecurrent flow irom from a source 01' alternating current to a load of thetype that has the properties oi a short circuit comprising an electricdischarge path having a control electrode and a plurality of principalelectrodes and a gaseous medium interpoad between said source and saidload through which current flows to said load, means for impresing apotential, proportional to the current iiow from said source when saidload is being supplied, between said control electrode and a principalelectrode 0! said path and means for impressing a direct currentpotential independent of the said current iiow but variable in magnitudein accordance with the load current desired between the said controlelectrode and the last said principal electrode. f

desired between the said control electrode and 23. Apparatus forvaryingthe supply of power from a source of alternating current to aload of the type that has the properties of a short circuit comprisingan electric discharge path having a control electrode and a plurality ofprincipal electrodes and a gaseous medium interposed between said'source and said load through which current flows to said load, means forimpressing a direct current potential, proportional to the current flowfrom said source when said lead is being supplied, between said controlelectrode and a principal electrode of said path and means forimpressing a direct-current potentialindependent of the said currentflow but variable in magnitude in accordance with the load current thelast said principal electrode.

24. Apparatus for varying the supply of power from a source ofalternating current to a load of the type that has the properties of ashort circuit comprising an electric discharge path having a controlelectrode, an anode and a cathode and a gaseous medium interposedbetween said source and said load through which current flows to saidload, means for impresing a direct current potential, proportional tothe current ilow from saidsourcewhensaidloadisbeingsupp ebe-' cuitcomprising an electric discharge path having a control electrode, ananode and a cathode and a gaseous medium interposed between said sourceand said load through which current flows to said load, means forimpressing a direct current potential proportional to the current flowfrom said source, when said 108d is being supplied between said controlelectrode and said cathode of said path and means for impressing adirect-current potential independent of the said current flow butvariable in magnitude in accordance with the load current desiredbetween the said control electrode and said cathode, said variablepotential being opposite in polarity to said proportional potential.

26. Apparatus for varyin the supply of power from a source ofalternating current to a load of the type that has the properties of ashort circuit comprising an electric discharge path having a controlelectrode, an anode and a cathode and a gaseous medium interposedbetween said source and said load through which current flows to saidload, means for impressing a direct current potential proportional tothe current flow from said source, when said load is being supplied,between said control electrode and said cathode oi said path and meansfor impressing a direct current potential independent of the saidcurrent flow but variable in magnitude in accordance with the loadcurrent desired between the said control electrode and said cathode,said variable potential being podtive in polarity and said proportionalpotential being negative in polarity.

WILLIAM M. GOODHUE. ROY B. POWER. Jn.

